This invention relates to building construction generally, and more particularly to a method and device for reinforcing metal roofs against wind lift.
As wind blows over a roof, the roof panels are subject to static air pressure from below, and a reduced or negative pressure above, according to Bernoulli's principle. Additionally, wind tends to "climb" the windward wall of a building, so that the leading edge of the roof on the windward side may actually have a positive angle of attack with respect to the wind, which increases the lifting force, particularly at the very edge and leading corners of the roof. The forces developed by high winds can be very large, and, depending on the height, orientation, roof slope, and other factors, these forces may be sufficient to cause seams and panel fasteners to fail. Once this happens, an entire portion of a roof can tear away, with potential disastrous results for the occupants or contents of the building. If the roof clips release, allowing the roof panels to break free completely, there is an additional hazard to people and objects downwind of the building. Therefore, we are concerned with strengthening roof panel seams and attachments, to prevent such failures.
We have determined that metal standing seam roofs fail, in many cases, during the uplift mode, due to concentrated loads developed at the location of clips which attach the roof panels to substructure. Such loads cause local distortion and buckling of some panels long before the panel itself fails in bending or other roof components fail. Our approach to solving this problem is to reinforce the panel-to-panel seams, and the points of load transfer to the structure, and thus prevent seam distortion, panel buckling, and seam failure. To do so, we have developed a seam clamp that maintains seam and corrugation geometry during uplift loading.